According to an old proverb, good things come to those who wait. That tends to be true in the stock market, at least for investors who buy shares of quality companies. Waiting, being patient, and holding on to these shares through painful downturns is the key to increasing one's wealth over long periods.

With that said, let's look at two healthcare stocks that can help patient investors become much richer: Medtronic (MDT 0.48%) and Merck (MRK -0.91%)

1. Medtronic 

Medtronic is one of the largest medical device companies in the world. It boasts a broad and diversified portfolio of products in several areas, including neuroscience, medical surgical, cardiovascular, and diabetes care. The company also operates in dozens of countries worldwide and generates steady revenue and earnings.

Still, Medtronic has encountered some headwinds lately, most notably during the pandemic, which disrupted the flow of operations in hospitals where the company's products are widely in use. Even beyond the outbreak, Medtronic has struggled to grow its revenue at a good clip for some time.

The company is looking to shake up its business, notably by divesting some parts. Medtronic will seek to divest its dialysis, respiratory interventions, and patient monitoring units. These make up roughly 8% of the company's revenue, so it's not insignificant. However, the move should help Medtronic focus and invest in areas with more high-growth potential.

One such area is diabetes care. Diabetes is a worsening health issue that affects 422 million worldwide. Medtronic has a portfolio of devices that simplify the lives of those with diabetes, which includes its MiniMed insulin pump series. The MiniMed 780G is one of the newest iterations. It does away with the need for painful fingersticks and can automatically adjust patients' sugar levels every five minutes.

That's incredibly convenient for patients with diabetes. Another potential long-term growth opportunity for Medtronic is robotic-assisted surgery. The company's Hugo RAS system has yet to be cleared in the U.S., although it is in use elsewhere. Given the advantages of RAS for patients, including faster recoveries and shorter hospital stays, this market should grow substantially over the years, something from which Medtronic can benefit.

Elsewhere, the company is looking to make good use of AI to improve its operations. Lastly, Medtronic is an excellent dividend stock. The company has raised its payouts for 45 consecutive years, so it is inching closer to Dividend King status. Medtronic shares currently yield 3.33%, about twice the S&P 500's 1.66%. Opting to reinvest dividends can help boost investors' returns, especially with a steady and reliable dividend payer like Medtronic. 

2. Merck 

Merck is one of the world's leading pharmaceutical companies. The drugmaker has crushed the broader market in the past year thanks to solid financial results led by its crown jewel, cancer medicine Keytruda. Merck's top-line growth reversed in the first quarter, with its sales dropping by 9% year over year to $14.5 billion. But that resulted from its antiviral COVID-19 therapy, Lagevrio, seeing decreasing demand.

Excluding Lagevrio, Merck's revenue rose by 11% year over year. That's an excellent performance for a pharmaceutical giant. And once again, Keytruda led the charge, generating $5.8 billion in sales, a 20% year-over-year increase. Yes, that means this product was responsible for more than 33% of Merck's revenue. While that could be a problem eventually, Keytruda is earning additional regulatory approvals and should be able to grow its sales at a good clip until it runs into U.S. patent expiration in 2028.

Recently, Merck reported encouraging results from a phase 2 clinical trial for its flagship drug in combination with Moderna's personalized cancer vaccine, mRNA-4157/V940, which reduced the risk of recurrence or death in melanoma patients. Keytruda routinely scores new clinical wins, and with many ongoing clinical trials, investors can expect more in the future.

Merck is also looking to diversify its lineup, which isn't just dependent on Keytruda right now. The company's vaccine division, led by HPV vaccines Gardasil and Gardasil 9, typically performs well. It boasts several other oncology products, including Lynparza and Lenvima, and its animal health unit. Merck recently announced plans to acquire Prometheus Biosciences for $10.8 billion in cash.

While Prometheus has no products on the market, it boasts several promising immunology programs. Just as important, Merck is somewhat quietly developing a subcutaneous formulation of Keytruda that could help extend its patent protection. Merck has what it takes to continue innovating and delivering new products while growing its revenue and earnings at a good clip, and recording solid returns for investors.